[llvm] [SelectionDAG] Prevent combination on inconsistent type in `combineCarryDiamond` (PR #84888)

[Simon Pilgrim via llvm-commits]

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@@ -3442,6 +3442,9 @@ static SDValue combineCarryDiamond(SelectionDAG &DAG, const TargetLowering &TLI,
     return SDValue();
   if (Opcode != ISD::UADDO && Opcode != ISD::USUBO)
     return SDValue();
+  // Guarantee identical type of CarryOut
+  if (N->getValueType(0) != Carry0.getValue(1).getValueType())
----------------
RKSimon wrote:

Most of this code implicitly assumes we're returning == MVT::i1, so maybe:
```cpp
if (N->getValueType(0) != MVT::i1 || 
    Carry0.getValue(1).getValueType() != MVT::i1 ||
    Carry1.getValue(1).getValueType() != MVT::i1)
  return SDValue();
```

https://github.com/llvm/llvm-project/pull/84888